The broad area of genetic regulation in eukaryotic cells is approached by study of normal chromatin structure and study of chromatin structure and function in cells treated with the thymidine analogue, 5- deoxybromouridine. Normal chromatin structure will be studied by isolation and characterization of the 11S subunits produced by nuclease digestion of liver nuclei. DNA conformation will be investigated by various spectroscopic methods. Histone-histone interactions will be studied by chemical modification techniques coupled with spectrophotometric methods; specifically, cross-linking and fluorescence energy transfer will be employed. Comparison of various parameters to those observed for chromatin isolated by conventional means will be made. Transcription of chromatin containing dBrU will be studied to characterize the reduced rate of RNA synthesis. The nature of the RNA produced will be evaluated by hybridization methodology. Specific isotonic labeling will be used to determine if the defect is in initiation or propagation of RNA chains. The effects of temperature change on RNA synthesis will be studied to test the hypothesis that dBrU specifically stabilizes A-T rich polymerase initiation sites.